1. Field of the Invention
The present invention is directed to a method for generating three-dimensional, multiply resolved volume images of an examination subject on the basis of two-dimensional projection images that can be registered (acquired) with an apparatus for producing radiation images, with a radiation source and a radiation receiver in an exposure procedure of the examination subject.
2. Description of the Prior Art
In methods of this type which are often utilized for generating and displaying images that can be medically interpreted, a number of two-dimensional projections are registered in order to obtain a good contrast resolution. A high number of projections, however, significantly increases the quantity of projection data, and it is expected that far more projections than is currently conventional, namely several hundred, will be registered in future applications. Additionally, the demands made on the transmission bandwidth, the processing and the storage of such data are also increasing explosively. One solution to this problem is to reduce the number of detector elements of the radiation detector in the underlying, two-dimensional detector matrix. This can be achieved by a technique referred to as “pixel binning”, whereby neighboring detector elements or pixels are combined and, for example, a signal average to be further-processed for this pixel cluster region is generated from the individual signals. Since, however, the detector area does not change, pixel binning results in a lower spatial resolution since a larger, effective pixel size is employed for covering the same detector region as was covered by multiple pixels. Disadvantageously, larger detector pixels or binned regions not only lower the spatial resolution at the detector but also the spatial resolution in the appertaining volume dataset. In applications wherein a high spatial resolution and a good recognizability of low-contrast subjects are required, a lowering of the spatial resolution is not desirable.
German OS 199 35 093 discloses a CT apparatus with a multi-line detector system wherein different columns of the detector system are connectable to a different number of electronics elements for the readout of the signals generated in the detector elements. Further, German OS 199 56 585 discloses a computed tomography method wherein an improved compromise between transmission bandwidth and image quality is achieved by combining the signals of at least two neighboring detector elements are combined into a measured value and a cyclic variation of the combination ensues from radiation source position-to-radiation source position. Further, German OS 195 24 858 discloses an X-ray generating system that is fashioned such that different image resolutions can be achieved in an economical way, an a-Si:H detector being provided for this purpose that is constructed of a number of sub-detectors lying in a plane, with respectively different resolutions.